New Gene Defect Causes Heavy Bones

Osteopetrosis is an inherited disorder whereby bones harden and become denser.

There are several different types of osteopetrosis caused by distinct genetic mutations, but not all the causative genetic mutations have been identified. In a study that appears in the April issue of the Journal of Clinical Investigation, researchers from the University of Antwerp, Belgium, identify PLEKHM1 as a new gene in which loss-of-function mutations cause osteopetrosis in humans and rats. Wim Van Hul and colleagues showed that a genetic mutation in PLEKHM1 caused the bone and tooth defects observed in incisors absent rats. A mutation in the same gene was associated with disease in a human patient with osteopetrosis. Bone cells known as osteoclasts from both this patient and incisors absent rats were impaired in their ability to destroy bone (which is essential for maintaining healthy bones). Further analysis suggested that PLEKHM1 was important for the transport of vesicles inside the osteoclasts, but further studies will be required before the precise molecular mechanism(s) by which PLEKHM1 loss-of-function mutations causes osteopetrosis is determined. (Source: Journal of Clinical Investigation : University of Antwerp : May 2007.)